Hybrid electric vehicles of the aforementioned type are known from DE 10 2004 041 637 A1. Described in said document is a method for controlling the activation of an energy source of a hybrid electric vehicle, in which a vehicle speed value is compared to a first threshold value and to a second threshold value. When the vehicle speed value is less than the first threshold value, the method establishes whether a vehicle brake has been disengaged. When the vehicle speed value is greater than the first threshold value and less than the second threshold value, the method establishes whether an additional acceleration is utilized. The energy source is activated when additional energy is required or when the vehicle brake has been disengaged. The energy source is deactivated when the brake is engaged or when no additional energy is utilized.
This known operating model is utilized, in particular, for controlling the different drives in the starting phase of a hybrid electric vehicle.